Why did Trump give Russia the green light to take over in Syria? He knows that Iran is gaining a foothold in that area now. maybe he's hoping this will motivate Israel to sign that peace deal.

Agreed, it sounds plausible.Also, Trump doesn't have that strong desire to go to war with Russia that seems to be in the minds and hearts of so many other American leaders, so I think this is his way of showing he wants cooperation with Russia.